1. Field of the Invention
This invention relates to a dimensionally recoverable elastomeric tubular article, a method for producing the article and a method of covering a substrate using the article. In particular, it relates to a dimensionally recoverable elastomeric tubular article comprising a radially expanded elastomeric inner member held in the expanded configuration by a relatively rigid outer restraining means.
2. Background Information
U.S. Pat. Nos. 4,070,746 and 4,135,553 to Evans and Wolfe, 4,179,320 and 4,287,012 to Midgley and Nyberg, and 4,338,970 to Krackeler and Wier, each disclose recoverable articles of the same general type as the articles of this invention. The recoverable article comprises an elastomer member held in an expanded condition by an outer restraining means. The elastomeric member is bonded to the outer restraint. In use, the article is positioned around a substrate to be covered and the elastomer member is released from the restraint. Due to the elastic properties of the expanded elastomeric member, it will then recover (or shrink) toward its unexpanded configuration and into contact with the substrate.
In U.S. Pat. No. 4,135,553, the elastomeric member is released from the restraint by applying a solvent which weakens the adhesive bond between the members. In U.S. Pat. No. 4,179,320, the elastomeric member is released from the restraint by peeling strips of the restraining means from the elastomer member. In U.S. Pat. No. 4,338,970, the elastomeric layer is released by breaking or segmenting the restraint and removing the pieces or segments from the elastomer member thereby allowing it to recover to its unexpanded configuration.
In U.S. Pat. No. 4,135,553 ('553), it is asserted that the bond between the elastomeric member and the restraint may be formed simply by adhesion of the elastomeric member to the restraint. In the practice of the '553 invention, it has been found that such a bond is inadequate to prevent premature recovery of the elastomeric member. The use of an adhesive to provide an adequate bond has been found to be necessary. It has also been found necessary to employ the fabrication procedures disclosed in U.S. Pat. No. 4,135,553. Such procedures involve forming the restraint, coating its inner surface with adhesive, forming the elastomeric member, coating its outer surface with adhesive, cross-linking the elastomer and expanding the elastomeric member into contact with the restraint. An alternate method is to form the elastomeric member and then injection mold the outer restraint around the member. Both these methods are non-continuous procedures in which each article must be manufactured individually.
This invention provides a method for the continuous manufacture of recoverable elastomer articles of this type. Prior attempts to coextrude the elastomeric member and the restraint were unsuccessful. The bond formed either had inadequate strength to restrain the elastomeric member from premature recovery, particularly if stored at temperatures of about 60.degree. C., or would not release the elastomeric member when solvent was applied. It has now been unexpectedly discovered that the incorporation of a segmented copolymer, as defined hereinafter, and optionally a tackifier into a thermoplastic material to be used for the restraint overcomes these problems and enables the continuous manufacture of dimensionally recoverable article of this type.